The invention relates generally to a technique for providing, in a system where various application apparatuses operate, a client device with a unified means for accessing data in all those application apparatuses.
Examples of conventional techniques for accessing, with a unified means, data in various application apparatuses include enterprise search technology, SRB (Storage Resource Broker), GNS (Global Namespace), XML (Extensible Markup Language), Gmail file system, and web services.
Enterprise search technology is designed to enable cross-application apparatus search of data existing in a system. The enterprise search technology is a technique for referring to data from each application apparatus, creating an index from keywords contained in the data, and returning a list of locations where searched for data is stored in response to a data search request from a client device.
When actual data is accessed in that technique, an interface provided by an application apparatus that manages the data is used, so no unified access method is provided. However, in this technique, data is converted into text and the thus converted text data is cached in a search server, so that a client device can refer to the text data with a unified method such as a text display tool (for enterprise search technology, see http://www.fastsearch.com/thesolution.aspx?m=376).
SRB and GNS technology provides a unified means for accessing data in geographically dispersed storage apparatuses. A storage apparatus is connected to the Internet and realizes data search or access from arbitrary locations. In this case, the storage apparatus is a target of a data search or access made mainly by a file server (for SRB technology, see http://www.sdsc.edu/srb/Pappres/SRB-overview.ppt; for GNS technology, see http://www.onstor.com/global_namespace.php).
XML technology unifies data formats into XML and has all application apparatuses provide an XML interface, thereby enabling a client device to access data in all application apparatuses in a unified XML format (for XML technology, see http://www.w3.org/TR/xml11/). In a manner similar to XML technology, web service technology has application apparatuses provide an interface for accessing data based on HTTP, thereby enabling a client device to access, using a unified web service interface, data in application apparatuses (for web service technology, see http://www.w3.org/TR/ws-arch/).
The Gmail file system is a technique for using a mail server as a file system. Files or management information used for managing a file system are stored as messages in a mail server (for Gmail file system technology, see http://richard.jones.name/google-hacks/gmail-file system/gmail-file system.html).
However, although the conventional enterprise search technology and Gmail file system technology enable reference to text-converted data using a unified method, data cannot be updated in the above technology.
The conventional SRB technology and the GNS technology can be used in storage apparatuses having a predetermined data access interface such as a file server, but cannot be used in application apparatuses using various interfaces. For example, a file sharing protocol called a network file system (NFS) is used as a data access interface.
In conventional XML technology, application apparatuses have to be made compliant with XML. Therefore, the technology cannot be used in application apparatuses that do not support existing XML. The web service technology also cannot be used in application apparatuses that do not support that technology.
As described above, with those conventional techniques, a client device cannot refer to or update, using a unified method, data in various application apparatuses, and this is inconvenient to a user of the client device.